Re: [RFC PATCH 03/21] i386/kvm: handle Xen HVM cpuid leaves

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 6/12/22 01:18, David Woodhouse wrote:
> On Mon, 2022-12-05 at 22:58 +0100, Philippe Mathieu-Daudé wrote:
>>>
>>> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
>>> index 22b681ca37..45aa9e40a5 100644
>>> --- a/target/i386/cpu.c
>>> +++ b/target/i386/cpu.c
>>> @@ -7069,6 +7069,8 @@ static Property x86_cpu_properties[] = {
>>>         * own cache information (see x86_cpu_load_def()).
>>>         */
>>>        DEFINE_PROP_BOOL("legacy-cache", X86CPU, legacy_cache, true),
>>> +    DEFINE_PROP_BOOL("xen", X86CPU, xen, false),
>>
>> Maybe name it 'xen-hvm'?
> 
> I think I'd prefer it to go away completely. If the *machine* has the
> Xen feature enabled (which I've made implicit in the 'xen-version'
> property), perhaps we should *always* disable 'expose_kvm' and enable
> the Xen CPUID leaves instead?

It would be silly to run a non-Xen guest on the Xen machine, so it is
not a bad idea :)

>>> +    DEFINE_PROP_BOOL("xen-vapic", X86CPU, xen_vapic, false),
>>
>> What happens if we use -cpu host,-kvm,+xen,-xen-vapic ?
> 
> That's sane; it does the Xen CPUID thing but doesn't advertise the
> vAPIC feature in the Xen CPUID leaves.

In which case we don't want to use the vAPIC?

Thanks,

Phil.